Implementing clone snapshots in a distributed storage system

ABSTRACT

A new snapshot of a storage volume is created by instructing computing nodes to suppress write requests. Once pending write requests from the computing nodes are completed, storage nodes create a new snapshot for the storage volume by allocating a new segment to the new snapshot and finalizes and performs garbage collection with respect to segments allocated to the previous snapshot. Subsequent write requests to the storage volume are then performed on the segments allocated to the new snapshot. An orchestration layer implements a multi-role application that is provisioned with virtualized storage and computation resources. A snapshot of the application may be created and used to rollback or clone the application. Clone snapshots of storage volumes may be gradually populated with data from prior snapshots to reduce loading on a primary snapshot.

RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 15/868,613filed Jan. 11, 2018 and U.S. application Ser. No. 15/868,652 filed Jan.11, 2018, which are incorporated herein by reference for all purposes.

BACKGROUND Field of the Invention

This invention relates to orchestration of roles in an applicationinstantiated in a distributed storage and computation system.

Background of the Invention

In many contexts, it is helpful to be able to return a database ordistributed application to an original state or some intermediate state.In this manner, changes to the distributed application or other databaseconfiguration parameters may be tested without fear of corruptingcritical data.

The systems and methods disclosed herein provide an improved approachfor creating snapshots of a database and returning to a previoussnapshot.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered limiting of its scope, the invention will be describedand explained with additional specificity and detail through use of theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram of a network environment forimplementing methods in accordance with an embodiment of the presentinvention;

FIG. 2 is a process flow diagram of a method for coordinating snapshotcreation with compute nodes and storage nodes in accordance with anembodiment of the present invention;

FIG. 3 is a schematic diagram illustrating the storage of data within astorage node in accordance with an embodiment of the present invention;

FIG. 4 is a process flow diagram of a method for processing writerequests in a storage node in accordance with an embodiment of thepresent invention;

FIG. 5 is a process flow diagram of a method for processing a snapshotinstruction by a storage node in accordance with an embodiment of thepresent invention;

FIG. 6 is a process flow diagram of a method for performing garbagecollection on segments in accordance with an embodiment of the presentinvention;

FIG. 7 is a process flow diagram of a method for reading data from asnapshot in accordance with an embodiment of the present invention;

FIG. 8 is a process flow diagram of a method for cloning a snapshot inaccordance with an embodiment of the present invention;

FIG. 9 illustrates a snapshot hierarchy created in accordance with anembodiment of the present invention;

FIG. 10 is a process flow diagram of a method for rolling back to aprior snapshot in accordance with an embodiment of the presentinvention;

FIG. 11 illustrates the snapshot hierarchy of FIG. 9 as modifiedaccording to the method of FIG. 10 in accordance with an embodiment ofthe present invention;

FIG. 12 is a process flow diagram of a method for reading from a clonesnapshot in accordance with an embodiment of the present invention;

FIG. 13 is a schematic block diagram of components for implementingorchestration of multi-role applications in accordance with anembodiment of the present invention;

FIG. 14 is a process flow diagram of a method for orchestrating thedeployment of a multi-role application in accordance with an embodimentof the present invention;

FIG. 15 is a process flow diagram of a method for implementingprovisioning constraints in accordance with an embodiment of the presentinvention;

FIG. 16 is a process flow diagram of a method for creating a snapshot ofa multi-role application in accordance with an embodiment of the presentinvention;

FIG. 17 is a process flow diagram of a method for rolling back amulti-role application in accordance with an embodiment of the presentinvention;

FIG. 18A is a diagram illustrating a thin clone in accordance with anembodiment of the present invention;

FIG. 18B is a diagram illustrating a thick clone in accordance with anembodiment of the present invention;

FIGS. 19A to 19E are process flow diagrams of methods for implementing adeferred thick clone in accordance with an embodiment of the presentinvention;

FIG. 20 is a diagram illustrating use of a test master clone inaccordance with an embodiment of the present invention;

FIG. 21 is a process flow diagram of a method for implementing a testmaster clone in accordance with an embodiment of the present invention;

FIG. 22 is a schematic diagram of an approach for implementing multipleinstances of a same executable using thin clones in accordance with anembodiment of the present invention;

FIG. 23 is a process flow diagram of a method for creating a bundletemplate in accordance with an embodiment of the present invention;

FIG. 24 is a process flow diagram of a method for implementing bundledependencies in accordance with an embodiment of the present invention;and

FIG. 25 is a schematic block diagram of an example computing devicesuitable for implementing methods in accordance with embodiments of theinvention.

DETAILED DESCRIPTION

Referring to FIG. 1, the methods disclosed herein may be performed usingthe illustrated network environment 100. The network environment 100includes a storage manager 102 that coordinates the creation ofsnapshots of storage volumes and maintains records of where snapshotsare stored within the network environment 100. In particular, thestorage manager 102 may be connected by way of a network 104 to one ormore storage nodes 106, each storage node having one or more storagedevices 108, e.g. hard disk drives, flash memory, or other persistent ortransitory memory. The network 104 may be a local area network (LAN),wide area network (WAN), or any other type of network including wired,fireless, fiber optic, or any other type of network connections.

One or more compute nodes 110 are also coupled to the network 104 andhost user applications that generate read and write requests withrespect to storage volumes managed by the storage manager 102 and storedwithin the memory devices 108 of the storage nodes 108.

The methods disclosed herein ascribe certain functions to the storagemanager 102, storage nodes 106, and compute node 110. The methodsdisclosed herein are particularly useful for large scale deploymentincluding large amounts of data distributed over many storage nodes 106and accessed by many compute nodes 110. However, the methods disclosedherein may also be implemented using a single computer implementing thefunctions ascribed herein to some or all of the storage manager 102,storage nodes 106, and compute node 110.

Referring to FIG. 2, the illustrated method 200 may be performed inorder to invoke the creation of a new snapshot. Other than a currentsnapshot, which is still subject to change, a snapshot captures thestate of a storage volume at a moment in time and is not altered inresponse to subsequent writes to the storage volume.

The method 200 includes receiving, by the storage manager 102 a requestto create a new snapshot for a storage volume. A storage volume asreferred to herein may be a virtual storage volume that may divided intoindividual slices. For example, storage volumes as described herein maybe 1 TB and be divided into 1 GB slices. In general, a slice and itssnapshot are stored on a single storage node 106, whereas a storagevolume may have the slices thereof stored by multiple storage nodes 106.

The request received at step 202 may be received from a human operatoror generated automatically, such as according to backup schedulerexecuting on the storage manager 102 or some other computing device. Thesubsequent steps of the method 200 may be executed in response toreceiving 202 the request.

The method 200 may include transmitting 204 a quiesce instruction to allcompute nodes 110 that are associated with the storage volume. Forexample, all compute nodes 110 that have pending write requests to thestorage volume. In some embodiments, the storage manager 102 may store amapping of compute nodes 110 to a particular storage volume used by thecompute nodes 110. Accordingly, step 204 may include sending 204 thequiesce instruction to all of these compute nodes. Alternatively, theinstruction may be transmitted 204 to all compute nodes 110 and includean identifier of the storage volume. The compute nodes 110 may thensuppress any write instructions referencing that storage volume.

The quiesce instruction instructs the compute nodes 110 that receive itto suppress 206 transmitting write requests to the storage nodes 106 forthe storage volume referenced by the quiesce instruction. The quiesceinstruction may further cause the compute nodes 110 that receive it toreport 208 to the storage manager 102 when no write requests are pendingfor that storage volume, i.e. all write requests issued to one or morestorage nodes 106 and referencing slices of that storage volume havebeen acknowledged by the one or more storage nodes 106.

In response to receiving the report of step 208 from one or more computenodes, e.g. all compute nodes that are mapped to the storage node thatis the subject of the snapshot request of step 202, the storage manager102 transmits 210 an instruction to the storage nodes 106 associatedwith the storage volume to create a new snapshot of that storage volume.Step 210 may further include transmitting 210 an instruction to thecompute nodes 110 associated with the storage volume to commence issuingwrite commands to the storage nodes 106 associated with the storagevolume. In some embodiments, the instruction of step 110 may include anidentifier of the new snapshot. Accordingly, subsequent input/outputoperations (IOPs) transmitted 214 from the compute nodes may referencethat snapshot identifier. Likewise, the storage node 106 may associatethe snapshot identifier with data subsequently written to the storagevolume, as described in greater detail below.

In response to receiving 210 the instruction to create a new snapshot,each storage node 106 finalizes 212 segments associated with the currentsnapshot, which may include performing garbage collection (GC), asdescribed in greater detail below. In addition, subsequent IOPs receivedby the storage node may also be processed 216 using the new snapshot asthe current snapshot, as is also described in greater detail below.

Referring to FIG. 3, the method by which slices are allocated,reassigned, written to, and read from may be understood with respect tothe illustrated data storage scheme. The data of the storage scheme maybe stored in transitory or persistent memory of the storage node 106,such as in the storage devices 108.

For each logical volume, the storage manager 102 may store and maintaina volume map 300. For each slice in the logical volume, the volume mapmay include an entry including a node identifier 302 identifying thestorage node 106 to which the slice is assigned and an offset 304 withinthe logical volume at which the slice begins. In some embodiments,slices are assigned both to a storage node 106 and a specific storagedevice hosted by the storage node 106. Accordingly, the entry mayfurther include a disk identifier of the storage node 106 referencingthe specific storage device to which the slice is assigned.

The remaining data structures of FIG. 3 are stored on each storage node106. The storage node 106 may store a slice map 308. The slice map 308may include entries including a local slice identifier 310 that uniquelyidentifies each slice of the storage node 106, e.g. each slice of eachstorage device hosted by the storage node 106. The entry may furtherinclude a volume identifier 312 that identifies the logical volume towhich the local slice identifier 310 is assigned. The entry may furtherinclude the offset 304 within the logical volume of the slice of thelogical volume assigned to the storage node 106.

In some embodiments, an entry in the slice map 308 is created for aslice of the logical volume only after a write request is received thatreferences the offset 304 for that slice. This further supports theimplementation of overprovisioning such that slices may be assigned to astorage node 106 in excess of its actual capacity since the slice isonly tied up in the slice map 308 when it is actually used.

The storage node 106 may further store and maintain a segment map 314.The segment map 314 includes entries either including or correspondingto a particular physical segment identifier (PSID) 316. For example, thesegment map 314 may be in an area of memory such that each address inthat area corresponds to one PSID 316 such that the entry does notactually need to include the PSID 316. The entries of the segment map314 may further include a slice identifier 310 that identifies a localslice of the storage node 106 to which the PSID 316 has been assigned.The entry may further include a virtual segment identifier (VSID) 318.As described in greater detail below, each time a segment is assigned tological volume and a slice of a logical volume, it may be assigned aVSID 318 such that the VSIDs 318 increase in value monotonically inorder of assignment. In this manner, the most recent PSID 316 assignedto a logical volume and slice of a logical volume may easily bedetermined by the magnitude of the VSIDs 318 mapped to the PSIDs 316. Insome embodiments, VSIDs 318 are assigned in a monotonically increasingseries for all segments assigned to volume ID 312. In other embodiments,each offset 304 and its corresponding slice ID 310 is assigned VSIDsseparately, such that each slice ID 310 has its own corresponding seriesof monotonically increasing VSIDs 318 assigned to segments allocated tothat slice ID 310.

The entries of the segment map 314 may further include a data offset 320for the PSID 316 of that entry. As described in greater detail below,when data is written to a segment it may be written at a first openposition from a first end of the segment. Accordingly, the data offset320 may indicate the location of this first open position in thesegment. The data offset 320 for a segment may therefore be updated eachtime data is written to the segment to indicate where the new first openposition is.

The entries of the segment map 314 may further include a metadata offset322. As described in detail below, for each write request written to asegment, a metadata entry may be stored in that segment at a first openposition from a second end of the segment opposite the first end.Accordingly, the metadata offset 322 in an entry of the segment map 314may indicate a location of this first open position of the segmentcorresponding to the entry.

Each PSID 316 corresponds to a physical segment 324 on a device hostedby the storage node 106. As shown, data payloads 326 from various writerequests are written to the physical segment 324 starting from a firstend (left) of the physical segment. The physical segment may furtherstore index pages 328 such that index pages are written starting from asecond end (right) of the physical segment 324.

Each index page 328 may include a header 330. The header 330 may becoded data that enables identification of a start of an index page 328.The entries of the index page 328 each correspond to one of the datapayloads 326 and are written in the same order as the data payloads 326.Each entry may include a logical block address (LBA) 332. The LBA 332indicates an offset within the logical volume to which the data payloadcorresponds. The LBA 332 may indicate an offset within a slice of thelogical volume. For example, inasmuch as the PSID 316 is mapped to aslice ID 310 that is mapped to an offset 304 within a particular volumeID 312, maps 308 and 314, and an LBA 332 within the slice may be mappedto the corresponding offset 304 to obtain a fully resolved addresswithin the logical volume.

In some embodiments, the entries of the index page 328 may furtherinclude a physical offset 334 of the data payload 326 corresponding tothat entry. Alternatively or additionally, the entries of the index page328 may include a size 336 of the data payload 326 corresponding to theentry. In this manner, the offset to the start of a data payload 326 foran entry may be obtained by adding up the sizes 336 of previouslywritten entries in the index pages 328.

The metadata offset 322 may point to the last index page 328 (furthestfrom right in illustrated example) and may further point to the firstopen entry in the last index page 328. In this manner, for each writerequest, the metadata entry for that request may be written to the firstopen position in the last index page 328. If all of the index pages 328are full, a new index page 328 may be created and stored at the firstopen position from the second end and the metadata for the write requestmay be added at the first open position in that index page 328.

The storage node 106 may further store and maintain a block map 338. Ablock map 338 may be maintained for each logical volume and/or for eachslice offset of each logical volume, e.g. for each local slice ID 310which is mapped to a slice offset and logical volume by slice map 308.The entries of the block map 338 map include entries corresponding toeach LBA 332 within the logical volume or slice of the logical volume.The entries may include the LBA 332 itself or may be stored at alocation within the block map corresponding to an LBA 332.

The entry for each LBA 332 may include the PSID 316 identifying thephysical segment 324 to which a write request referencing that LBA waslast written. In some embodiments, the entry for each LBA 332 mayfurther indicate the physical offset 334 within that physical segment324 to which the data for that LBA was written. Alternatively, thephysical offset 324 may be obtained from the index pages 328 of thatphysical segment. As data is written to an LBA 332, the entry for thatLBA 332 may be overwritten to indicate the physical segment 324 andphysical offset 334 within that segment 324 to which the most recentdata was written.

In embodiments implementing multiple snapshots for a volume and slice ofa volume, the segment map 314 may additionally include a snapshot ID 340identifying the snapshot to which the PSID 316 has been assigned. Inparticular, each time a segment is allocated to a volume and slice of avolume, the current snapshot identifier for that volume and slice of avolume will be included as the snapshot ID 340 for that PSID 316.

In response to an instruction to create a new snapshot for a volume andslice of a volume, the storage node 106 will store the new currentsnapshot identifier, e.g. increment the previously stored currentsnapshot ID 340, and subsequently allocated segments will include thecurrent snapshot ID 340. PSIDs 316 that are not filled and are allocatedto the previous snapshot ID 340 may no longer be written to. Instead,they may be finalized or subject to garbage collection (see FIGS. 5 and6).

FIG. 4 illustrates a method 400 for executing write instructions by astorage node 106, such as write instructions received from anapplication executing on a compute node 110.

The method 400 includes receiving 402 a write request. The write requestmay include payload data, payload data size, and an LBA as well asfields such as a slice identifier, a volume identifier, and a snapshotidentifier. Where a slice identifier is included, the LBA may be anoffset within the slice, otherwise the LBA may be an address within thestorage volume.

The method 400 may include evaluating 404 whether a PSID 316 isallocated to the snapshot referenced in the write request and whetherthe physical segment 324 corresponding to the PSID 316 (“the currentsegment”) has space for the payload data. In some embodiments, as writerequests are performed with respect to a PSID 316, the amount of datawritten as data 326 and index pages 328 may be tracked, such as by wayof the data offset 320 and metadata offset 322 pointers. Accordingly, ifthe amount of previously-written data 326 and the number of allocatedindex pages 328 plus the size of the payload data and its correspondingmetadata entry exceeds the capacity of the current segment it may bedetermined to be full at step 404.

If the current segment is determined 404 to be full, the method 400 mayinclude allocating 406 a new PSID 316 as the current PSID 316 and itscorresponding physical segment 324 as the current segment for thesnapshot referenced in the write request. In some embodiments, thestatus of PSIDs 316 of the physical storage devices 108 may be flaggedin the segment map 314 as allocated or free as a result of allocationand garbage collection, which is discussed below. Accordingly, a freePSID 316 may be identified in the segment map 314 and flagged asallocated.

The segment map 314 may also be updated 408 to include a slice ID 310and snapshot ID 340 mapping the current PSID 316 to the snapshot ID,volume ID 312, and offset 304 included in the write request. Uponallocation, the current PSID 316 may also be mapped to a VSID (virtualsegment identifier) 318 that will be a number higher than previouslyVSIDs 318 such that the VSIDs increase monotonically, subject, ofcourse, to the size limit of the field used to store the VSID 318.However, the size of the field may be sufficiently large that it is notlimiting in most situations.

The method 400 may include writing 410 the payload data to the currentsegment. As described above, this may include writing 410 payload data326 to the free location closest to the first end of the currentsegment.

The method 400 may further include writing 412 a metadata entry to thecurrent segment. This may include writing the metadata entry (LBA, size)to the first free location closest to the second end of the currentsegment. Alternatively, this may include writing the metadata entry tothe first free location in an index page 328 that has room for it orcreating a new index page 328 located adjacent a previous index page328. Steps 410, 412 may include updating one or more pointers or tablethat indicates an amount of space available in the physical segment,such as a pointer 320 to the first free address closest to the first endand a pointer 322 to the first free address closest to the second end,which may be the first free address before the last index page 328and/or the first free address in the last index page. In particular,these pointers may be maintained as the data offset 320 and metadataoffset in the segment map 314 for the current PSID 316.

The method 400 may further include updating 416 the block map 338 forthe current snapshot. In particular, for each LBA 332 referenced in thewrite request, an entry in the block map 338 for that LBA 332 may beupdated to reference the current PSID 316. A write request may write toa range of LBAs 332. Accordingly, the entry for each LBA 332 in thatrange may be updated to refer to the current PSID 316.

Updating the block map 338 may include evaluating 414 whether an entryfor a given LBA 332 referenced in the write request already exists inthe block map 338. If so, then that entry is overwritten 418 to refer tothe current PSID 316. If not, an entry is updated 416 in the block map318 that maps the LBA 332 to the current PSID 316. In this manner, theblock map 338 only references LBAs 332 that are actually written to,which may be less than all of the LBAs 332 of a storage volume or slice.In other embodiments, the block map 338 is of fixed size and includesand entry for each LBA 332 regardless of whether it has been written topreviously. The block map 338 may also be updated to include thephysical offset 334 within the current segment to which the data 326from the write request was written.

In some embodiments, the storage node 106 may execute multiple writerequests in parallel for the same LBA 332. Accordingly, it is possiblethat a later write can complete first and update the block map 338whereas a previous write request to the same LBA 332 completes later.The data of the previous write request is therefore stale and the blockmap 338 should not be updated.

Suppressing of updating the block map 338 may be achieved by using theVSIDs 318 and physical offset 334. When executing a write request for anLBA, the VSID 318 mapped to the segment 324 and the physical offset 334to which the data is to be, or was, written may be compared to the VSID318 and offset 334 corresponding to the entry in the block map 338 forthe LBA 332. If the VSID 318 mapped in the segment map 314 to the PSID316 in the entry of the block map 338 corresponding to the LBA 332, thenthe block map 338 will not be updated. Likewise, if the VSID 318corresponding to the PSID 316 in the block map 338 is the same as theVSID 318 for the write request and the physical offset 334 in the blockmap 338 is higher than the offset 334 to which the data of the writerequest is to be or was written, the block map 338 will not be updatedfor the write request.

As a result of steps 414-418, the block map 338 only lists the PSID 316where the valid data for a given LBA 332 is stored. Accordingly, onlythe index pages 328 of the physical segment 324 mapped to the PSID 316listed in the block map 338 need be searched to find the data for agiven LBA 332. In instances where the physical offset 334 is stored inthe block map 338, no searching is required.

FIG. 5 illustrates a method 500 executed by a storage node 106 inresponse to the new snapshot instruction of step 210 for a storagevolume. The method 500 may be executed in response to an explicitinstruction to create a new snapshot or in response to a write requestthat includes a new snapshot ID 340. The method 500 may also be executedwith respect to a current snapshot that is still being addressed by newwrite requests. For example, the method 500 may be executed periodicallyor be triggered based on usage.

The method 500 may include allocating 502 a new PSID 316 and itscorresponding physical segment 324 as the current PSID 316 and currentsegment for the storage volume, e.g., by including a slice ID 310corresponding to a volume ID 312 and offset 304 included in the newsnapshot instruction or the write request referencing the new snapshotID 340. Allocating 502 a new segment may include updating 504 an entryin the segment map 314 that maps the current PSID 316 to the snapshot ID340 and a slice ID 310 corresponding to a volume ID 312 and offset 304included in the new snapshot instruction.

As noted above, when a PSID 316 is allocated, the VSID 318 for that PSID316 may be a number higher than all VSIDs 318 previously assigned tothat volume ID 312, and possibly to that slice ID 310 (where slices haveseparate series of VSIDs 318). The snapshot ID 340 of the new snapshotmay be included in the new snapshot instruction or the storage node 106may simply assign a new snapshot ID that is the previous snapshot ID 340plus one.

The method 500 may further include finalizing 506 and performing garbagecollection with respect to PSIDs 316 mapped to one or more previoussnapshots IDs 340 for the volume ID 312 in the segment map 314, e.g.,PSIDs 316 assigned to the snapshot ID 340 that was the current snapshotimmediately before the new snapshot instruction was received.

FIG. 6 illustrates a method 600 for finalizing and performing garbagecollection with respect to segment IDs 340 for a snapshot (“the subjectsnapshot”), which may include the current snapshot or a previoussnapshot. The method 600 may include marking 602 as valid latest-writtendata for an LBA 332 in the PSID 316 having the highest VSID 318 in thesegment map 314 and to which data was written for that LBA 332. Marking602 data as valid may include making an entry in a separate table thatlists the location of valid data or entries for metadata in a givenphysical segment 324 or setting a flag in the metadata entries stored inthe index pages 328 of a physical segment 324, e.g., a flag thatindicates that the data referenced by that metadata is invalid or valid.

Note that the block map 338 records the PSID 316 for the latest versionof the data written to a given LBA 332. Accordingly, any references tothat LBA 332 in the physical segment 324 of a PSID 316 mapped to alower-numbered VSID 318 may be marked 604 as invalid. For the physicalsegment 324 of the PSID 316 in the block map 338 for a given LBA 332,the last metadata entry for that LBA 332 may be found and marked asvalid, i.e. the last entry referencing the LBA 332 in the index page 328that is the last index page 328 including a reference to the LBA 332.Any other references to the LBA 332 in the physical segment 324 may bemarked 604 as invalid. Note that the physical offset 334 for the LBA 332may be included in the block map 334, so all metadata entries notcorresponding to that physical offset 334 may be marked as invalid.

The method 600 may then include processing 606 each segment ID S of thePSIDs 316 mapped to the subject snapshot according to steps 608-620. Insome embodiments, the processing of step 606 may exclude a current PSID316, i.e. the last PSID 302 assigned to the subject snapshot. Asdescribed below, garbage collection may include writing valid data froma segment to a new segment. Accordingly, step 606 may commence with thePSID 316 having the lowest-valued VSID 318 for the subject snapshot. Asany segments 324 are filled according to the garbage collection process,they may also be evaluated to be finalized or subject to garbagecollection as described below.

The method 600 may include evaluating 608 whether garbage collection isneeded for the segment ID S. This may include comparing the amount ofvalid data in the physical segment 324 for the segment ID S to athreshold. For example, if only 40% of the data stored in the physicalsegment 324 for the segment ID S has been marked valid, then garbagecollection may be determined to be necessary. Other thresholds may beused, such as value between 30% and 80%. In other embodiments, theamount of valid data is compared to the size of the physical segment324, e.g., the segment ID S is determined to need garbage collection ifthe amount of valid data is less than X % of the size of the physicalsegment 324, where X is a value between 30 and 80, such as 40.

If garbage collection is determined 608 not to be needed, the method 600may include finalizing 610 the segment ID S. Finalizing may includeflagging the segment ID S in the segment map 314 as full and no longeravailable to be written to. This flag may be stored in another tablethat lists finalized PSIDs 316.

If garbage collection is determined 608 to be needed, then the method600 may include writing 612 the valid data to a new segment. Forexample, if the valid data may be written to a current PSID 316, i.e.the most-recently allocated PSID 316 for the subject snapshot, until itscorresponding physical segment 324 full. If there is no room in thephysical segment 324 for the current PSID 316, step 612 may includeassigning a new PSID 316 as the current PSID 316 for the subjectsnapshot. The valid data, or remaining valid data, may then be writtento the physical segment 324 corresponding to the current PSID 316 forthe subject snapshot.

Note that writing 612 the valid data to the new segment maybe processedin the same manner as for any other write request (see FIG. 4) exceptthat the snapshot ID used will be the snapshot ID 340 of the subjectsnapshot, which may not be the current snapshot ID. In particular, themanner in which the new PSID 316 is allocated to the subject snapshotmay be performed in the same manner described above with respect tosteps 406-48 of FIG. 4. Likewise, the manner in which the valid data iswritten to the current segment may be performed in the same manner asfor steps 410-412 of FIG. 4. In some embodiments, writing of valid datato a new segment as part of garbage collection may also include updatingthe block map with the new location of the data for an LBA 332, such asaccording to steps 414-418 of FIG. 4. When the physical segment 324 ofthe current PSID 316 is found to be full, it may itself be subject tothe process 600 by which it is finalized or subject to garbagecollection.

After the valid data is written to a new segment, the method 600 mayfurther include freeing 614 the PSID Sin the segment map 314, e.g.,marking the entry in segment map 314 corresponding to PSID S as free.

The process of garbage collection may be simplified for PSIDs 316 thatare associated with the subject snapshot in the segment map 314 but arenot listed in the block map 338 with respect to any LBA 332. Thephysical segments 324 of such PSIDs 316 do not store any valid data.Entries for such PSIDs 316 in the segment map 314 may therefore simplybe deleted and marked as free in the segment map 314

FIG. 7 illustrates a method 700 that may be executed by a storage node106 in response to a read request. The read request may be received froman application executing on a compute node 110. The read request mayinclude such information as a snapshot ID, volume ID (and/or slice ID),LBA, and size (e.g. number of 4 KB blocks to read).

The following steps of the method 700 may be initially executed usingthe snapshot ID 340 included in the read request as “the subjectsnapshot,” i.e., the snapshot that is currently being processed tosearch for requested data. The method 700 includes receiving 702 theread request by the storage node 106 and identifying 704 one or morePSIDs 316 in the segment map 314 assigned to the subject snapshot andsearching 706 the metadata entries for these PSIDs 316 for references tothe LBA 332 included in the read request.

The searching of step 706 may be performed in order of decreasing VSID318, i.e. such that the metadata entries for the last allocated PSID 316is searched first. In this manner, if reference to the LBA 332 is found,the metadata of any previously-allocated PSIDs 316 does not need to besearched.

Searching 706 the metadata for a PSID 316 may include searching one ormore index pages 328 of the physical segment 324 corresponding to thePSID 316. As noted above, one or more index pages 328 are stored at thesecond end of the physical segment 324 and entries are added to theindex pages 328 in the order they are received. Accordingly, thelast-written metadata including the LBA 332 in the last index page 328(furthest from the second end of the physical segment 324) in which theLBA 332 is found will correspond to the valid data for that LBA 332. Tolocate the data 326 corresponding to the last-written metadata for theLBA 332 in the physical segment 324, the sizes 336 for allpreviously-written metadata entries may be summed to find a startaddress in the physical segment 324 for the data 326. Alternatively, ifthe physical offset 334 is included, then the data 326 corresponding tothe metadata may be located without summing the sizes 336.

If reference to the LBA 332 is found 708 in the physical segment 324 forany of the PSIDs 316 allocated to the subject snapshot, the data 326corresponding to the last-written metadata entry including that LBA 332in the physical segment 324 mapped to the PSID 316 having the highestVSID 318 of all PSIDs 316 in which the LBA is found will be returned 710to the application that issued the read request.

If the LBA 332 is not found in the metadata entries for any of the PSIDs316 mapped to subject snapshot, the method 700 may include evaluating712 whether the subject snapshot is the earliest snapshot for thestorage volume of the read request on the storage node 106. If so, thenthe data requested is not available to be read and the method 700 mayinclude returning 714 a “data not found” message or otherwise indicatingto the requesting application that the data is not available.

If an earlier snapshot than the subject snapshot is present for thestorage volume on the storage node 106, e.g., there exists at least onePSID 316 mapped to a snapshot ID 340 that is lower than the snapshot ID340 of the subject snapshot ID, then the immediately preceding snapshotID 340 will be set 716 to be the subject snapshot and processing willcontinue at step 704, i.e. the PSIDs 316 mapped to the subject snapshotwill be searched for the LBA 332 in the read request as described above.

The method 700 is particularly suited for reading data from snapshotsother than the current snapshot that is currently being written to. Inthe case of a read request from the current snapshot, the block map 338may map each LBA 332 to the PSID 316 in which the valid data for thatLBA 332 is written. Accordingly, for such embodiments, step 704 mayinclude retrieving the PSID 332 for the LBA 332 in the write requestfrom the block map 338 and only searching 706 the metadata correspondingto that PSID 316. Where the block map 338 stores a physical offset 334,then the data is retrieved from that physical offset within the physicalsegment 314 of the PSID 336 mapped to the LBA 332 of the read request.

In some embodiments, the block map 332 may be generated for a snapshotother than the current snapshot in order to facilitate executing readrequests, such as where a large number of read requests are anticipatedin order to reduce latency. This may include searching the index pages328 of the segments 324 allocated to the subject snapshot and itspreceding snapshots to identify, for each LBA 332 to which data has beenwritten, the PSID 316 having the highest VSID 318 of the PSIDs 316having physical segments 324 storing data written to the each LBA 332.This PSID 316 may then be written to the block map 318 for the each LBA332. Likewise, the physical offset 334 of the last-written data for thatLBA 332 within the physical segment 324 for that PSID 316 may beidentified as described above (e.g., as described above with respect tosteps 704-716).

Referring to FIG. 8, in some instances it may be beneficial to clone astorage volume. This may include capturing a current state of aprincipal copy of a storage volume and making changes to it withoutaffecting the principal copy of the storage volume. For purposes of thisdisclosure a “principal copy” or “principal snapshot” of a storagevolume refers to an actual production copy that is part of a series ofsnapshots that is considered by the user to be the current, official, ormost up-to-date copy of the storage volume. In contrast, a clonesnapshot is a snapshot created for experimentation or evaluation butchanges to it are not intended by the user to become part of theproduction copy of the storage volume. Stated differently, only onesnapshot may be a principal snapshot with respect to an immediatelypreceding snapshot, independent of the purpose of the snapshot. Anyother snapshots that are immediate descendants of the immediatelypreceding snapshot are clone snapshots.

The illustrated method 800 may be executed by the storage manager 102and one or more storage nodes 106 in order to implement thisfunctionality. The method 800 may include receiving 802 a cloneinstruction and executing the remaining steps of the method 800 inresponse to the clone instruction. The clone instruction may be receivedby the storage manager 102 from a user or be generated according to ascript or other program executing on the storage manager 102 or a remotecomputing device in communication with the storage manager 102.

The method 800 may include recording 804 a clone branch in a snapshottree. For example, referring to FIG. 9, in some embodiments, for eachsnapshot that is created for a storage volume, the storage manager 102may create a node S1-S5 in a snapshot hierarchy 900. In response to aclone instruction, the storage manager 102 may create a clone snapshotand branch to a node A1 representing the clone snapshot. In theillustrated example, a clone instruction was received with respect tothe snapshot of node S2. This resulted in the creation of clone snapshotrepresented by node A1 that branches from node S2. Note node S3 and itsdescendants are also connected to node S2 in the hierarchy.

In some embodiments, the clone instruction may specify which snapshotthe clone snapshot is of In other embodiments, the clone instruction maybe inferred to be a snapshot of a current snapshot. In such embodiments,a new principal snapshot may be created and become the current snapshot.The previous snapshot will then be finalized and be subject to garbagecollection as described above. The clone will then branch from theprevious snapshot. In the illustrated example, if node S2 representedthe current snapshot, then a new snapshot represented by node S3 wouldbe created. The snapshot of node S2 would then be finalized and subjectto garbage collection and clone snapshot represented by A1 would becreated and node A1 would be added to the hierarchy as a descendent ofnode S2.

In some embodiments, the clone node A1, and possibly its descendants A2to A4 (representing subsequent snapshots of the clone snapshot), may bedistinguished from the nodes S1 to S5 representing principal snapshots,such as by means of a flag, a classification of the connection betweenthe node A1 and node S2 that is its immediate ancestor, or by storingdata defining node A1 in a separate data structure.

Following creation of a clone snapshot, other principal snapshots of thestorage volume may be created and added to be represented in thehierarchy by one or more nodes S2 to S5. A clone may be created of anyof these snapshots and represented by additional clone nodes. In theillustrated example, node B1 represents a clone snapshot of the snapshotrepresented by node S4. Subsequent snapshots of the clone snapshot arerepresented by nodes B1 to B3.

Referring again to FIG. 8, the creation of a clone snapshot on thestorage node 106 may be performed in the identical manner as for anyother snapshot, such as according to the methods of FIGS. 2 through 6.In particular, one or more segments 806 may be allocated to the clonesnapshot on storage nodes 106 storing slices of the cloned storagevolume and mapped to the clone snapshot. IOPs referencing the clonesnapshot may be executed 808, such as according to the method 400 ofFIG. 4.

In some instances, it may be desirable to store a clone snapshot on adifferent storage node 106 than the principal snapshots. Accordingly,the method 800 may include allocating 806 segments to the clone snapshoton the different storage node 106. This may be invoked by sending a newsnapshot instruction referencing the clone snapshot (i.e., an identifierof the clone snapshot) to the different storage node 106 and instructingone or more compute nodes 110 to route IOPs for the clone snapshot tothe different storage node 106.

The storage node 102 may store in each node of the hierarchy, dataidentifying one or more storage nodes 106 that store data for thesnapshot represented by that node of the hierarchy. For example, eachnode may store or have associated therewith one or more identifiers ofstorage nodes 106 that store a particular snapshot ID for a particularvolume ID. The node may further map one or more slice IDs (e.g., sliceoffsets) of a storage volume to one storage nodes 106 storing data forthat slice ID and the snapshots for that slice ID.

Referring to FIG. 10, one of the benefits of snapshots is the ability tocapture the state of a storage volume such that it can be restored at alater time. FIG. 10 illustrates a method 1000 for rolling back a storagevolume to a previous snapshot, particularly for a storage volume havingone or more clone snapshots.

The method 1000 includes receiving 1002, by the storage manager 102, aninstruction to rollback a storage volume to a particular snapshot SN.The method 1000 may then include processing 1004 each snapshot that is arepresented by a descendent node of the node representing snapshot SN inthe snapshot hierarchy, i.e. snapshots SN+1 to SMAX, where SMAX is thelast principal snapshot that is a descendent of snapshot SN (each“descendent snapshot”). For each descendent snapshot, processing 1004may include evaluating 1006 whether the each descendent is an ancestorof a node representing a clone snapshot. If not, then the storagemanager 102 may instruct all storage nodes 106 storing segments mappedto the descendent snapshot to free 1008 these segments, i.e. deleteentries from the segment map referencing the descendent snapshot andmarking corresponding PSIDs 316 as free in the segment map 314.

If the descendent snapshot is found 1006 to be an ancestor of a clonesnapshot, then step 1008 is not performed and the snapshot and anysegments allocated to it are retained.

FIG. 11 illustrates the snapshot hierarchy following execution of themethod 1000 with respect to the snapshot represented by node S3. As isapparent, snapshot S5 has been removed from the hierarchy and anysegments corresponding to these snapshots will have been freed on one ormore storage nodes 106.

However, since node S4 is an ancestor of clone node B1, it is notremoved and segments corresponding to it are not freed on one or morestorage nodes in response to the roll back instruction. Inasmuch as eachsnapshot contains only data written to the storage volume after it wascreated, previous snapshots may be required to recreate the storagevolume. Accordingly, the snapshots of nodes S3 to S1 are needed tocreate the snapshot of the storage volume corresponding to node B1.

Subsequent principal snapshots of the storage volume will be added asdescendants of the node to which the storage volume was rolled back. Inthe illustrated example, a new principal snapshot is represented by nodeS6 that is an immediate descendent of node S3. Node S4 is only presentdue to clone node B1 and therefore may itself be classified as a clonenode in the hierarchy in response to the rollback instruction of step1002.

Note that FIG. 11 is a simple representation of a hierarchy. There couldbe any number of clone snapshots, clones of clone snapshots anddescendent snapshots of any of these snapshots represented by nodes of ahierarchy. Accordingly, to roll back to a particular snapshot of aclone, the method 1000 is the same, except that descendants of the clonesnapshot are treated the same as principal snapshots and clones of anyof these descendants are treated the same as a clone snapshot.

Referring to FIG. 12, the illustrated method 1200 may be used to executea read request with respect to a storage volume that is represented by ahierarchy generated as described above with respect to FIGS. 8 through11. The illustrated method 1200 may also be executed with respect to astorage volume that includes only principal snapshots that aredistributed across multiple storage nodes, i.e., all the segmentscorresponding to snapshots of the same slice of the storage volume arenot located on the same storage node 106. In that case, the hierarchystored on the storage manager 102 stores the location of the segmentsfor each snapshot and therefore enables them to be located.

The method 1200 may be executed by a storage node 106 (“the currentstorage node”) with information retrieved from the storage manager 102as noted below. The method 1200 may include receiving 1202 a readrequest, which may include such information as a snapshot ID, volume ID(and/or slice ID), LBA, and size (e.g. number of 4 KB blocks to read).

Note that the read request may be issued by an application executing ona compute node 110. The compute node 110 may determine which storagenode 106 to transmit the read request using information from the storagemanager 102. For example, the compute node 110 may transmit a request toobtain an identifier for the storage node 102 storing data for aparticular slice and snapshot of a storage volume. The storage managermay then obtain an identifier and/or address for the storage node 106storing that snapshot and slice of the storage volume from thehierarchical representation of the storage volume and return it to therequesting compute node 110. For example, the storage manager 102 mayretrieve this information from the node in the hierarchy representingthe snapshot included in the read request.

In response to the read request, the current storage node performs thealgorithm illustrated by subsequent steps of the method 1200. Inparticular, the method 1200 may include identifying 1204 segmentsassigned to the snapshot ID of the read request in the segment (“thesubject snapshot”).

The method 1200 may include searching 1206 the metadata of the segmentsidentified in step 1204 for the LBA of the read request. If the LBA isfound, the data from the highest numbered segment having the LBA in itsmetadata is returned, i.e. the data that corresponds to the last-writtenmetadata entry including the LBA.

If the LBA is not found in any of the segments mapped to subjectsnapshot, then the method 1200 may include evaluating 1212 whether thesubject snapshot is the earliest snapshot on the current storage node.If not, then steps processing continues at step 1204 with the previoussnapshot set 1214 as the subject snapshot.

Steps 1204-1214 may be performed in the same manner as for steps 704-714of the method 700, including the various modifications and variationsdescribed above with respect to the method 700.

In contrast to the method 700, if the LBA is not found in any of thesegments corresponding to the subject snapshot for any of the snapshotsevaluated, then the method 1200 may include requesting 1216 a location,e.g. storage node identifier, where an earlier snapshot for the volumeID or slice ID is stored. In response to this request, the storagemanager 102 determines an identifier of a storage node 106 storing thesnapshot corresponding to the immediate ancestor of the earliestsnapshot stored on the current storage node in the hierarchy. Thestorage manager 102 may determine an identifier of the storage node 106relating to the immediate-ancestor snapshot and that stores data for aslice ID and volume ID of the read request as recorded for the ancestornearest ancestor node in the hierarchy of the node corresponding to theearliest snapshot stored on the current storage node.

If the current storage node is found 1218 to be the earliest snapshotfor the storage volume ID and/or slice ID of the read request, then thedata the storage manager 102 may report this fact to the storage node,which will then return 1220 a message indicating that the requested LBAis not available for reading, such as in the same manner as step 714 ofthe method 700.

If another storage node stores an earlier snapshot for the volume IDand/or slice ID of the read request, then the read request may betransmitted 1222 to this next storage node by either the current storagenode or the storage manager 102. The processing may then continue atstep 1202 with the next storage node as the current storage node. Theread request transmitted at step 1222 may have a snapshot ID set to thelatest snapshot ID for the storage volume ID and or slice ID of theoriginal read request.

The method 1200 may be performed repeatedly across multiple storagenodes 106 until the earliest snapshot is encountered or the LBA of theread request is located.

Referring to FIG. 13, storage according to the above-described methodsand systems may be incorporated into an application-orchestrationapproach. In the illustrated approach, an orchestration layer 1300implements a bundled application 1302 including a plurality of roles. Inthe following description, “bundled application” refers to a bundle ofapplications as implemented using the orchestration layer. A “role” isan instance of an executable that is managed by the orchestration layeras described herein as part of the bundled application. Accordingly, a“role” may itself be a standalone application, such as a database,webserver, blogging application, or any other application. Examples ofroles include the roles used to implement multi-role applications suchas CASSANDRA, HADOOP, SPARK, DRUID, SQL database, ORACLE database,MONGODB database, WORDPRESS, and the like. For example, in HADOOP, rolesmay include one or more of a named node, data node, zookeeper, andAMBARI server.

The orchestration layer 1300 may implement a bundled application 1302defining roles and relationships between roles as described in greaterdetail below. The orchestration layer 1300 may execute on a computingdevice of a distributed computing system (see e.g., FIG. 1), such as ona compute node 110, storage node 106, a computing device executing thefunctions of the storage manager 102, or some other computing device.Accordingly, actions performed by the orchestration layer may beinterpreted as being performed by the computing device executing theorchestration layer 1300.

The bundled application 1302 may include a manifest 1304 that definesthe roles of the bundled application 1302, which may include identifiersof roles and possibly a number of instances for each role identified.The manifest 1304 may define dynamic functions define how the number ofinstances of particular role may grow or shrink depending on usage. Theorchestration layer 1300 may then create or remove instances for a roleas described below as indicated by usage and one or more functions forthat role. The manifest 1304 may define a topology of the bundledapplication 1302, i.e. the relationship between roles, such as servicesof a role that are accessed by another role.

The bundled application 1302 may include provisioning 1306. Theprovisioning 1306 defines the resources of storage nodes 106 and computenodes 110 required to implement the bundle. The provisioning 1306 maydefine resources for the bundle as a whole or for individual roles.Resources may include a number of processors (e.g., processing cores),an amount of memory (e.g., RAM (random access memory), an amount ofstorage (e.g., GB (gigabytes) on a HDD (Hard Disk Drive) or SSD (SolidState Drive)). As described below, these resources may be provisioned ina virtualized manner such that the bundled application 1302 andindividual roles 1312 are not informed of the actual location orprocessing and storage resources and are relieved from anyresponsibility for managing such resources. In particular, storageresources may be virtualized by the storage manager 102 using themethods described above such that storage volumes are allocated and usedwithout requiring the bundled application 1302 or roles to manage theunderlying storage nodes 106 and storage device 108 on which the data ofthe storage volumes is written.

Provisioning 1306 may include static specification of resources and mayalso include dynamic provisioning functions that will invoke allocationof resources in response to usage of the bundled application. Forexample, as a database fills up, additional storage volumes may beallocated. As usage of a bundled application increases, additionalprocessing cores and memory may be allocated to reduce latency.

A bundled application 1302 may further include configuration parameters1308. Configuration parameters may include variables and settings foreach role of the bundle. The configuration parameters are defined by thedeveloper of the role and therefore may include any example of suchparameters for any application known in the art. The configurationparameters may be dynamic or static. For example, some parameters may bedependent on resources such as an amount of memory, processing cores, orstorage. Accordingly, these parameters may be defined as a function ofthese resources. The orchestration layer will then update suchparameters according to the function in response to changes inprovisioning of those resources that are inputs to the function. Forexample, CASSANDRA defines a variable Max_Heap_Size that is normally setto half the memory limit. Accordingly, as the memory provisioned for aCASSANDRA role increases, the value of Max_Heap_Size may be increased tohalf the increased memory.

The bundled application 1302 may further include action hooks 1310 forvarious actions that may be taken with respect to the bundledapplication and/or particular roles of the bundled applications. Actionsmay include some or all of stopping, starting, restarting, takingsnapshots, cloning, and rolling back to a prior snapshot. For eachaction, one or more action hooks may be defined. A hook is aprogrammable routine that is executed by the orchestration layer whenthe corresponding action is invoked. A hook may specify a script ofcommands or configuration parameters input to one or more roles in aparticular order. Hooks for an action may include a pre-action hook(executed prior to implementing an action), an action hook (executed toactually implement the action), and a post action hook (executedfollowing implementation of the action).

The bundled application 1302 may define a plurality of roles 1312. Eachrole may include one or more provisioning constraints. As noted above,the bundled application 1302 and roles 1312 are not aware of theunderlying storage nodes 106 and compute nodes 110 inasmuch as these arevirtualized by the storage manager 102 and orchestration layer 1300.Accordingly, any constraints on allocation of hardware resources may beincluded in the provisioning constraints 1314. As described in greaterdetail below, this may include constraints to create separate faultdomains in order to implement redundancy and constraints on latency.

The role 1312 may define a name space 1316. A name space 1316 mayinclude variables, functions, services, and the like implemented by arole. In particular, interfaces and services exposed by a role may beincluded in the name space. The name space may be referenced through theorchestration layer 1300 by an addressing scheme, e.g. <Bundle ID>.<RoleID>.<Name>. In some embodiments, references to the namespace 1316 ofanother role may be formatted and processed according to the JINJAtemplate engine or some other syntax. Accordingly, each role 1312 mayaccess the variables, functions, services, etc. in the name space 1316of another role 1312 on order to implement a complex applicationtopology. In some instances, credentials for authorizing access to arole 1312 may be shared by accessing the namespace 1316 of that role.

A role 1312 may further include various configuration parameters 1318defined by the role, i.e. as defined by the developer that created theexecutable for the role. As noted above, these parameters 1318 may beset by the orchestration layer 1300 according to the static or dynamicconfiguration parameters 1308. Configuration parameters may also bereferenced in the name space 1316 and be accessible (for reading and/orwriting) by other roles 1312.

Each role 1312 may include a container 1320 executing an instance 1322of the application for that role. The container 1320 may be avirtualization container, such as a virtual machine, that defines acontext within which the application instance 1322 executes,facilitating starting, stopping, restarting, and other management of theexecution of the application instance 1322. Containers 1320 may includeany container technology known in the art such as DOCKER, LXC, LCS, KVM,or the like. In a particular bundled application 1302, there may becontainers 1320 of multiple different types in order to take advantageof a particular container's capabilities to execute a particular role1312. For example, one role 1312 of a bundled application 1302 mayexecute a DOCKER container 1320 and another role 1312 of the samebundled application 1302 may execute an LCS container 1320.

Note that a bundled application 1302 as configured in the foregoingdescription may be instantiated and used or may be saved as a templatethat can be used and modified later.

FIG. 14 illustrates a method 1400 for executing a bundled application1302 using the orchestration layer 1300. The method 1400 may includeprovisioning 1402 storage and computation resources according to theprovisioning 1306. This may include allocating storage volumes accordingto the storage requirements, assigning the storage volumes to storagenodes 106, and selecting a compute node 110 or storage node 106providing the required computational resources (processor cores andmemory).

The method 1400 may include creating 1404 role instances for the roles1312 defined by the bundled application 1302. As described above, thismay include creating a container 1320 and instantiating the applicationinstance 1322 of the role 1312 within the container 1320. The order inwhich instances 1322 are created and started may be defined in themanifest 1304.

The method 1400 may include configuring 1406 each role according to theconfiguration parameters 1308, including executing any includedfunctions to determine values for dynamic parameters. As noted above,starting a bundled application 1302 may further include setting up 1408the roles 1312 to reference resources in the name space 1316 of anotherrole 1312. For example, a webserver may be configured to access adatabase by referencing configuration parameters and servicesimplemented by the database.

The method 1400 may further include executing 1410 any hooks 1310defined for the initial startup of the bundled applications.Accordingly, pre-startup, startup, and post startup hooks may beexecuted. Some or all of the functions of steps 1402-1410 may be definedas part of the pre-startup hook. Other functions may also be performedprior to steps 1402-1408 as defined by a pre-startup hook.

The actual commencement of execution of the instances 1322 of thebundled application 1302 may be performed in an order specified by thestartup hook and may include performing any attendant functions of theseinstances 1322 as specified by the startup hook. Following startup, oneor more other actions may be performed as specified by the developer inthe post-startup hook. These actions may invoke functions of theinstances 1322 themselves or executed by the orchestration layer 1300outside of the instances 1322, such as with respect to an operatingsystem executing the containers 1320 for the instances 1322.

The bundled application 1302 may then be accessed 1412 in order toperform the programmed functionality of the application instances 1322.As usage occurs, processing resources will be loaded and storage may befilled. The method 1400 may further include adjusting 1414 provisioningaccording to this usage and may performed adjustment to configurationparameters of the roles 1312 according to this provisioning as definedby the provisioning 1306 and configuration functions 1308.

As noted above, instances of roles may also be created or removedaccording to usage. Accordingly, where indicate by the manifest 1304,instances 1322 for a role 1312 may be created according to steps1402-1410 throughout execution of the bundled application 1302 asdefined by one or more dynamic functions in the manifest 1304 for thatrole 1312.

Referring to FIG. 15, the illustrated method 1500 may be used toimplement provisioning constraints 1314 for a role 1312 or constraintsfor an entire bundled application 1302. The method 1500 may be executedby the orchestration layer 1300, storage manager 102, or a combinationof the two.

The method 1500 may include receiving 1502 the provisioning constraint1314 for one or more roles 1312 of the bundled application 1302 anddetermining 1504 whether the constraint 1314 specify one or both of afault domain constraint and a latency constraint.

If a latency constraint is found 1506 to be included for a role 1312,then computational resources and storage resources to be provisioned forthe role 1312 may be constrained 1508 to be co-located. In particular,latency may be specified in terms of (a) a minimum network delay, (b) aminimum network throughput, (c) an explicit constraint to placecomputation and storage resources in the same subnetwork, or (d) anexplicit constraint to place computation and storage resources on thesame node, i.e. a hybrid compute and storage node 110, 106 that performsthe functions of both types of nodes with a single computer.

This constraint may be used by the orchestration layer to assigncomputing and storage resources to roles 1312 and storage volumes of thebundled application. For example, one or more storage volumes for therole 1312 will be assigned to storage nodes 106 that can either (a) meetthe latency requirement with respect to compute nodes 110 allocated tothe role 1312 (b) also provide the computational resources required forthe role 1312.

The orchestration layer 1300 may include a resource manager in thataccounts for all of the compute storage requirements and constraints andcreates a resource allocation plan. This plan describes the virtualnodes (containers 1320) that make up the bundled application 1302. Eachvirtual node has allocations of processor cores, memory and storagevolumes. The resource manager determines the compute host (compute node110 or hybrid node) for each virtual node and a set of devices for eachstorage volume of the virtual node. The orchestration layer 1300 sendsthis mapping of the storage volumes to physical devices to the storagemanager 102, which implements the storage allocation.

If the constraint for a role 1312 is found 1510 to include a faultdomain constraint, then storage volumes for the role 1312 may bedistributed 1512 among the storage nodes 106 of the distributed storagesystem 100 according to this requirement. For example, if storage volumeB is a redundant (e.g., replica or backup) copy of storage volume A, thefault domain constraint may indicate this fact. Accordingly, the storagemanager 102 may assign storage volume B to a different storage node 106than storage volume A. Various degrees of constraint may be specified.For example, a fault domain constraint may simply require a differentstorage device 108 but not require a different storage node 106. A faultdomain constraint may require that storage nodes 106 to which storagevolumes are assigned by in separate subnetworks, different geographiclocations, or have some other degree of separation. Similar fault domainconstraints may be specified for roles 1312, which may be constrained toexecute on different compute nodes 110 in order to provide redundantservices and reduce downtime.

The provisioning constraints 1502 based on fault domains and/or latencymay be combined with one or more other constraints. For example, aperformance constraint (IOPs/second) for a storage node may be imposed.Accordingly, only those compute nodes meeting the performancerequirement and the fault domain and/or latency requirements will beselected for provisioning.

As noted above, provisioning 1306 may define a processing requirement,such as a number of processing cores and an amount of storage for arole. Accordingly, compute nodes 110 may be selected at step 1508 suchthat both the latency requirement and processing requirement are met.

Referring to FIG. 16, the illustrated method 1600 may be executed by theorchestration layer 1302 with respect to a bundled application 1302 inorder to create a snapshot of the bundled application 1302 that can belater restored (see the method 1700 of FIG. 17).

The method 1600 may include flushing 1602 application buffers to disk.In many instances, performance of an application is accelerated bymaintaining data in a cache in memory, such that data in the cache isaccessed and updated without requiring writing to a disk in manyinstances, as known in the art. Accordingly, this buffer may be flushed1602 to disk by writing all valid data (i.e., not outdated due to asubsequent write) in the cache to the storage device 108 to which thatdata is addressed, e.g., to which the storage volume referenced by thedata is assigned.

In a like manner, a file system flush may be performed 1604. Performinga file system flush may include ensuring that all IOPs pending to beperformed by the file system have been executed, i.e. written to disk.As for step 1602, data written to a cache for the file system this isvalid may be written to a storage device 108 to which the data isaddressed, e.g., to which the storage volume referenced by the data isassigned.

The method 1600 may then include freezing 1606 the application instances1322 of each role 1312. In particular, inasmuch as each instance 1322 isexecuting within container 1320, the containers 1320 for the roles 1312may be instructed to pause execution of each instance 1322. This mayinclude stopping execution and saving a state of execution of eachinstance 1322 (state variables, register contents, program pointers,function stack, etc.).

The method 1600 may further include creating 1608 a snapshot of storagevolumes provisioned for the bundled application. This may includeexecuting the method 200 of FIG. 2 or any of the above-describedapproaches for implementing a snapshot of a storage volume.

The method 1600 may further include creating 1610 a topology snapshotfor the bundled application 1302. The topology of an application mayinclude some or all of the following information as constituted at thetime of executing step 1610 a listing of the roles 1312, which mayinclude one or more instances 1322 of the same role 1322, relationshipsbetween application instances 1322 of roles 1312 (name spacecross-references, configuration parameters), storage volumes assigned toroles 1312, or other information that describes the topology of thebundled application 1302. Applications may create metadata describingtheir state of operation. This data may also be saved as part of thetopology snapshot.

After the snapshot is created according to the method 1600, theapplication instances may be resumed, with the application itself notsuffering any down time in some embodiments. The bundled application1302 may then continue to operate. If desired, the application may thenbe rolled back to the snapshot created according to the method 1600, asdescribed below with respect to FIG. 17.

FIG. 17 illustrates a method 1700 for rolling back a bundled application1302 to a snapshot, such as a snapshot created according to the method1600. The method 1700 may be executed by one or both of theorchestration layer 1300 and the storage manager 102.

The method 1700 includes receiving 1702 a rollback instruction, such asfrom an administrator desiring to return to a stable version of thebundled application 1302. The remaining steps of the method 1300 may beexecuted in response to the rollback instruction.

The method 1700 may include rolling 1704 back storage volumes assignedto the bundled application 1302 to the snapshots created for thesnapshot of the bundled application 1302 (e.g., at step 1608 of themethod 1600). This may include executing the method 1000 of FIG. 10 orperforming any other approach for rolling back a storage volume to aprior state.

The method 1700 may include restoring 1706 application instances fromthe application snapshot. As described above with respect to step 1606of the method 1600, an application instance 1322 may be frozen.Accordingly, data describing a state of execution of the applicationinstance 1322 may be reloaded into a container 1302 for that instance.If needed, the container for that application instance 1322 may becreated and the instance 1322 loaded into it prior to loading the stateof execution. This is particularly the case where the number ofapplication instances has changed since the application snapshot wascreated.

The method 1700 may further include restoring 1708 the applicationtopology saved for the bundled application at step 1610. Accordingly,relationships between application instances 1322 of roles 1312 (namespace cross-references, configuration parameters), storage volumesassigned to roles 1312, or other information that describes the topologyof the bundled application 1302 may be restored as it was at the timethe application snapshot was created

The method 1700 further include executing 1710, 1712, 1714 a pre-restarthook, restart hook, and post restart hook defined for the bundledapplication. As described above, each hook may be a routine defined by adeveloper to be executed for a particular action, restarting in thiscase. In step 1712, execution of the instances 1322 for the roles 1322may be restarted, along with any other actions specified by thedeveloper in the restart hook.

The bundled application 1302 as restored at steps 1704-1714 may then beaccessed 1716 as defined by the programming of the application instancesand the restored application topology.

Note that the snapshot of the bundled application 1302 may be restartedon different storage and compute nodes 106, 110 than those on which thebundled application 1302 was executing when the snapshot was created.Accordingly, the application snapshot may be restarted as a clone of thebundled application 1302 or moved to different hardware when executingthe method 1700.

In some instances, the hooks of steps 1710, 1712, 1714 may be differentwhen the application snapshot is being restarted as a clone as desiredby a developer. For example, a developer may desire to scale the cloneapplication to increase or decrease a number of databases, number ofpartitions of a database, or other aspect of the clone application.Accordingly, the hooks of steps 1710, 1712, 1714 may implement routinesto implement this increase or decrease.

For example, some applications are able to automatically detect thenumber of partitions of a database. In such instances, some or all ofthe hooks 1710, 1712, 1714 may reduce the number of partitions in adatabase of the clone applications and rely on the application todiscover this change. In other instances, some or all of the hooks 1710,1712, 1714 may be programmed to configure an application to access thedatabase with the reduced number of partitions where the application isunable to configure itself.

Referring to FIGS. 18A and 18B, a storage volume may be cloned in theform of a clone snapshot, such as according to the approach describedabove with respect to FIGS. 8 through 12.

FIG. 18A illustrates the approach of FIGS. 8 through 12, which isreferred to herein as a “thin” clone. In this approach, a segment Eallocated to the clone snapshot S2 after creation of the clone snapshotis written only to the clone snapshot. Segments A-D that were written tosnapshot S1 prior to creation of clone snapshot S2 are not copied tosnapshot S1. As noted above, snapshot S2 may be on a different storagenode than snapshot S1. As described above with respect to FIG. 12, readsfrom an application 1800 for segments A-D will therefore be routed tothe storage node storing snapshot S1. Reads for segment E can beprocessed locally.

This results in increase latency for these reads and increases loadingof the storage node 106 storing snapshot S1. In the case where snapshotS1 is a production snapshot and snapshot S2 is only for testing, thisloading may be undesirable. However, copying the segments A-D tosnapshot S2 will also result in loading of the storage node 106 storingsnapshot S1.

FIG. 18B illustrates a “thick” clone wherein the segments A-D are copiedto snapshot S2. In this manner, all reads are handled by the storagenode 106 storing the snapshot S2 and the production storage node 106storing S1 is not loaded. However, the process of copying the segmentsA-D to snapshot S2 will also result in loading of the storage node 106storing snapshot S1.

FIG. 19A illustrates a method 1900 a for implementing a “deferred thickclone” snapshot wherein segments of snapshot S1 are gradually copied tosnapshot S2 while avoiding impacting performance of the productionstorage node 106 storing snapshot S1. The method 1900 a may be executedby the storage node 106 storing the snapshot S2 (“the clone node”) incooperation with the storage node 106 storing the snapshot S1 (“theprimary node”). The segments that are copied may have correspondingVSIDs as described above with respect to FIG. 3. The association of aVSID to a segment may maintained for the copy of the segment on theclone node. As described above, a storage volume may be divided intoslices that may reside on different storage nodes 106. Accordingly, themethod 1900 a may be executed separately for each slice of the storagevolume.

The method 1900 a may include creating 1902 a deferred thick clonesnapshot. This may include creating a thin clone snapshot (FIG. 8, FIG.18A) S2. Creating 1902 a deferred thick clone snapshot may includeallocating physical segments 324 and corresponding PSIDs 316 for eachsegment to be copied, such as prior to the segments being copied. Insome embodiments, a user may instruct that a pre-existing thin clonesnapshot is to be converted to a deferred thick clone snapshot accordingto the method 1900 a.

The segment map 314 may be updated to include the slice ID 310 (mappedto offset within cloned storage volume per slice map 308), and VSID 318,and possibly other information shown in FIG. 3, for each segment to becopied. The snapshot ID 340 in the segment map 340 may be set equal toS2, i.e. the snapshot identifier for the clone snapshot. The segment map314 may be updated either prior to copying or each PSID 316 entry may beupdated when the corresponding segment is copied to the physical segment324 for that PSID 316.

The method 1900 a may include setting 1904 a load limit, e.g., a limiton how much copying traffic the clone node may impose on the primarynode. The load limit may be specified in terms of a number of bytes persecond, a number of segments that may be copied at any one time, orother limits. The load limit may be time dependent. For example, atnight or other periods of low usage, the load limit may be raised sinceproduction usage of the clone node will not be significantly impaired.

The load limit may also specify a maximum number of read IOPs that maybe requested from the primary node in a given time period, e.g., maximumIOPs/second limit.

The method 1900 a may include evaluating 1906 whether there is a hitimbalance for any of the segments that remain to be copied from theprimary node to the clone node. In particular, if a large number of readrequests are being routed to the primary node for a particular segment,then copying of that segment will reduce loading of the primary node andreduce latency for the clone node.

Accordingly, reads routed to the primary node may be tabulated for eachsegment referenced. Copying of segments may then be ordered according tothe number of reads, with a segment having a higher number of readsbeing copied before a segment with a lower number. Where N segments maybe in process of being copied simultaneously, then the N segments withthe N highest read counts may be selected 1908 for copying first. Whereno read imbalance exists, e.g., there is no significant difference inthe number of reads per segment, the segments may be copied in order,e.g. in order of increasing VSIDs. What is significant may be apredetermined value. For example, where the highest read count is lessthan X percent of the average read count, the imbalance may be deemedinsignificant, where X is a value between 1.1 and 2 or some otherpredetermined value greater than one.

In some instances, heavily used storage volumes and segments of astorage volume may be known by a developer based on the applicationtopology, e.g., log files with heavy write usage and low read usage maybe copied last whereas heavily read data may be read first. Accordingly,the ordering of copying of segments may be specified by a developer inorder to copy those segments with a high hit rate first.

The method 1900 a may include evaluating 1910 whether the primary node1910 has spare capacity. For example, the primary node 1910 may transmitloading information, e.g. IOPs per second, to the clone node. Forexample, where this loading falls below a predetermined threshold, e.g.less than Y percent of the total IOP/second capacity of the primarynode, then the load limit for copying segments may be increased 1912,where Y is predetermined value less than 100, such as 70. The amount ofthe load limit may be set to some predetermined function of the unusedIOP/second capacity of the primary node, e.g. such that no more than Zpercent of the capacity is used, such as Z=90 percent.

In a like manner, if the primary node is determined 1914 to be loaded,the load limit may be decreased, e.g. decreased such that the amount ofunused capacity of the primary remains below an acceptable value, e.g.,such that the load limit plus production loading of the primary node isless than Z percent.

Note that steps 1910-1916 may be performed at the storage device 108level. Accordingly, loading of a storage device 108 is evaluated 1910,1914 and the load limit increased 1912 or decreased 1916 based on theloading in the same manner described above.

Note also that the evaluations of steps 1906, 1910, 1914 may beperformed at the container 1320 level. In particular, storage volumesallocated to instances 1322 that are generating higher read trafficrelative to other instances 1322 may be copied before storage volumesallocated to the other instances 1322.

Copying of segments according to the load limit may be performed 1918.Steps 1906-1918 may be performed repeatedly until all segments are found1920 to have been copied.

With reference to FIG. 3, Once all segments are copied the block map 338may be rebuilt 1922 according to the copied segments. In particular,metadata (e.g., index pages 328) of the copied segments may be evaluatedto determine the physical offset 334 of LBAs referenced in the copiedsegments. The entry for each LBA may then be updated to include the PSID316 where the copied segments was written and the physical offset 334for that LBA. As noted above, a block map 338 may be maintained for eachslice of a logical storage volume. Accordingly, updating 1922 the blockmap may be performed for each slice referenced by the copied segments.

As noted above, the block map 338 indicates the location of the latestwritten data addressed to an LBA. Accordingly, references to an LBA 332in a copied segment will not cause updating of the entry in the blockmap 338 for that LBA 332 where a later version of data has been writtento that LBA 332.

For example, where a copied segment referencing an LBA 332 has a lowerVSID than the VSID 318 mapped to the PSID 316 in the block map for thatLBA 332, the entry for that LBA 332 in the block map 338 will not beupdated for that copied segment.

The method 1900 a may be performed in the context of cloning a bundledapplication 1302. Accordingly, the rollback method of FIG. 17 may beperformed on different hardware then that on which the bundledapplication 1302 was executing when an application snapshot was createdin order to create a clone of the bundled application. In suchinstances, storage volumes may be cloned as either thin clones, thickclones, or deferred thick clones. The clone application may thereforecontinue to access storage nodes 106 provisioned for the originalbundled application 1302 until a deferred thick clone has completedcopying of data from the original bundled application.

Referring to FIG. 19B, in another approach, a deferred thick clonesnapshot may be implemented according to the method 1900 b. The method1900 b may include creating 1902 a deferred thick clone snapshot (“thesubject snapshot”) of a storage volume (“the subject volume”), such asin the same manner as for the method 1900 a. The subject snapshot may beon a different storage node 106 (“the clone node”) than the storage node106 (“the parent node”) storing the parent snapshot of the subjectvolume of which the subject snapshot is a deferred thick clone snapshot.

When a read request is received 1924 for the subject snapshot of thesubject storage volume, the method 1900 b may include evaluating 1926whether an address (e.g., LBA and slice offset) referenced by the readrequest has been previously written to after creation of the subjectsnapshot. If so, then the read request is executed 1928 with respect tothe subject snapshot by the clone node (e.g., see FIG. 12).

If not, then the read request is transmitted 1930 to the parent node,which then processes the read request and returns the read data to asource of the read request from step 1924. Steps 1926-1930 may beexecuted according to the approach described above with respect to FIG.12. The parent node may further include a component that intercepts 1932the read data and writes 1934 the read data to the clone node, e.g.,issues a write request to the subject snapshot, the write requestincluding the read data and the address (e.g., LBA and slice offset)from the read request. This write request is referred to herein has aninternal clone write (ICW) and may be flagged or otherwise bedistinguishable from other types of writes, such as writes from userapplications.

The read request that is transmitted at step 1930 may include anindication that it is a pass through read request from the subjectsnapshot. Accordingly, the parent node may determine based on thisindication that writing 1934 of the read data is required as an ICW.

Upon receiving the ICW, the clone node writes 1934 the read data to theclone snapshot (e.g., see FIG. 4). Note that there is a possibility thatthe data may be written to the same LBA and slice offset of the subjectsnapshot before the ICW is received. In such cases, the ICW isdiscarded, since the data written to the subject snapshot at the sameLBA and slice offset referenced by the ICW is more current.

FIG. 19C illustrates an alternative method 1900 c for implementing adeferred thick clone. The method 1900 c may include performing steps1902-1930 according to any of the variations for performing these stepsdescribed above with respect to the method 1900 c.

The method 1900 c may further include incrementing 1936, by the clonenode, a slice counter for a slice referenced by the read request of step1924 for each read request that is found 1926 to not reference datawritten to the subject snapshot after creation of the subject snapshot.

If the counter for a slice is found 1938 to exceed a threshold, thenthat slice is copied 1940 from the parent snapshot to the clonesnapshot, i.e. copied to the clone node. Copying 1940 may includeindividually copying all of the segments of the slice from the parentnode to the clone node.

If the threshold is not met, then one of two approaches may be used. Ina first approach, no copying is performed. In a second approach, theread data of the parent snapshot is intercepted 1932 and written 1934 tothe clone snapshot in the same manner as for the method 1900 b.

FIGS. 19D and 19E describe approaches for executing write requests for adeferred thick clone implemented according to FIG. 19C. Referringspecifically to FIG. 19D, the illustrated method 1900 d may includereceiving 1942, by the clone node, a user write request to the subjectsnapshot, i.e. a write request from a user application that is otherthan a write request performed as part of copying a segment or slice (aninternal clone write (ICW)) from the parent snapshot.

The method 1900 d may include evaluating 1944 whether an ICW is inprocess that references the same LBA and slice offset as the writerequest of step 1942. If so, the write request is held 1946 and is notexecuted until no conflicting ICW is in process. In this manner, writesare executed in the proper order and the data of the write request ofstep 1942 is not overwritten by the ICW.

If and when no conflicting ICW is found 1944 to be in process, the writerequest may be executed. The write request may be executed in the mannerdescribed above with respect to FIG. 4 with the changes indicated inFIG. 19D. In particular, if a current segment is found 1948 to be full,a new segment is allocated 1950 and assigned 1952 a VSID in a clone IDrange. The write request may then be executed 1954.

By assigning writes to the clone snapshot VSIDs in a unique range ofvalues, it is possible to distinguish between segments that have beenwritten to the subject snapshot and those that were copied to thesubject snapshot from the parent snapshot according to method of FIG.19C.

FIG. 19E illustrates a method 1900 e for processing internal clonewrites (ICW) of segments from the parent snapshot. The ICW is received1956 and one or more segments are allocated 1958 to the subject snapshotfor storing the data from the ICW. The allocated segments may then eachbe assigned 1960 a unique VSID from a parent ID range that does notoverlap the clone ID range (see FIG. 4). Accordingly, where datareferencing the LBA is found in segments with VSIDs in the clone IDrange and the parent ID range, the valid data can readily be determinedto be in the VSIDs in the clone ID range. In some embodiments, the cloneID range is higher than the parent ID range such that segment with thehighest VSID of those segments containing data for an LBA will containthe most current data for that LBA.

In some embodiments, the parent ID range is for a range of valuessufficiently large such that no overlap with the dine ID range willoccur, e.g. some multiple of the total number of segments in a slice,e.g. a multiple between 1 and 2. Note also that the new VSIDs assignedat step 1960 may preserve the ordering of the VSIDs from the parentsnapshot, i.e. where a first segment has a higher VSID than a secondsegment in the parent snapshot the VSIDs assigned to the first segmentat step 1960 will also be higher than the VSID assigned to the secondsegment at step 1960.

The segments of the parent snapshot received at step 1956 may then bewritten 1962 to the segments allocated at step 1912. The segment map 314may be updated to map the copied segments to the PSIDs 316 to which theywere written as well as the other information shown in FIG. 3 for anentry in the segment map 314.

The block map 338 for each slice referenced in the ICW may then beupdated for each LBA referenced in the one or more segments of the ICW.Where an entry already exists in the block map 338 for an LBA referencedin an ICW, the entry is not overwritten in some embodiments, since thisindicates that a user write has occurred after creation of the subjectsnapshot and should not be overwritten by data from the parent snapshot.

If the block map 338 is lost and must be reconstructed, current data foran LBA may be identified by identifying the most current data in thesegments assigned VSIDs in the clone ID range (the last written data tothe segment with the highest VSID). If an LBA is not referenced insegments assigned VSIDs in the clone ID range, then the most currentdata in the segments of the subject snapshot assigned VSIDs in theparent ID range is the current data for that LBA (the last written datato the segment with the highest VSID).

FIG. 20 illustrates an example application of a deferred thick clonesnapshot. A production database 2000 may store segments A-D. Theproduction database may be implemented according to the virtualizationapproach described with respect to FIGS. 1 through 12 or may be anyother type of database, such as SQL (structured query language), MYSQL,ORACLE database, or any other database approach known in the art.

A test master 2002 may be created for the database 2000, where the testmaster 2002 is a deferred thick clone snapshot according to the method1900 a. Accordingly, the segments A-D are copied to the test master 2002over time and according to load limits.

In the future, users that wish to test clones of the database 2000 maythereafter make thin clone snapshots 2004 of the test master 2002. Inthis manner, read requests will be routed to the test master 2002 andnot the production database 2000 if the requested data has not beenwritten to the thin clone snapshot 2004. Any number of thin clonesnapshots 2004 may be created. In some instances, the test master 2002may be maintained current, i.e. be updated according to all changes tothe production database rather than simply copying data written previousto creation of the test master 2002.

As for FIG. 18B, an application 1800 accessing the thin clone snapshot2004 may have reads routed to the clone node hosting the test master2002 or to the node hosting the production database 2000 if the segmentscorresponding to the reads are located there. Once all segments arecopied to the test master 2002, reads from the application 1800 willthen be forwarded only to the clone node hosting the test master 2002.

FIG. 21 illustrates a method 2100 for using a test master 2002. Themethod 2100 may be executed by the storage nodes implementing the testmaster 2002 and clone snapshot 2004.

The method 2100 may include receiving 2102 a first namespacespecification for a production database 2000. The namespace of adatabase may define data labels that may be used to search and requestdata in the database. As used herein, a namespace may also refer to a“tablespace” or “schema” as used in other database terminology orimplementations. The first namespace specification may include aspecification of less than all of the namespaces of the productiondatabase 2000. For example, a database may define various shards ofdata. The first namespace specification may therefore reference lessthan all of the shards of the production database 2000.

The method 2100 may then include creating 2104 a test master 2002 thatis a deferred thick clone of the production database 2000 that islimited to the first namespace specification and then populating 2106the test master 2002 as a deferred thick clone. Creating a deferredthick clone may be performed according to the approach described abovewith respect to some or all of FIGS. 19A-19E.

In the illustrated embodiment, only data belonging to the firstnamespace will be cloned. In this manner, a user may select part of adatabase for testing thereby further reducing the copying load on theproduction database 2000. In some instances, the first namespacespecification will include an entirety of the production database 2000.

The method 2100 may then include receiving 2108 a second namespacespecification and creating 2110 a thin clone snapshot 2004 of the testmaster 2002 for data according to the second namespace specification. Asdescribed above, the thin clone will write new data addressed to thethin clone snapshot 2004 to the clone node hosting the snapshot 2004.The second namespace specification may be the same as or different fromthe first namespace specification. Accordingly, only data in the secondnamespace will be accessible by reading and writing to the thin clonesnapshot 2004.

Read requests for the thin clone snapshot 2004 may then be processed2112. As described above, read requests for data written prior tocreation 2110 of the snapshot 2004 will be routed to the clone nodehosting the test master 2002. For segments that have not yet been copiedto the test master 2002, read requests addressed to them will be routedto the host of the production database 2000 until those segments arecopied to the test master subject to load limits. Read requests for datawritten to the thin clone snapshot 2004 after its creation will be readfrom the clone node hosting the snapshot 2004, which may be the same asor different from the clone node hosting the test master 2002.

Note that a thick clone or deferred thick clone of the test master 2002may be created. This is particularly the case where the test master 2002needs to be moved to a higher performance device. For example, a cloneof the test master 2002 may be created on a higher performance deviceand an original instance of the test master 2002 may be shut down.

Note that the method 2100 may be executed in the context of cloning abundled application 1302, which includes cloning its storage volumes(see description of FIG. 17). Accordingly, the method 2100 may beimplemented by some or all of the hooks 1710, 1712, 1714 during theprocess of cloning application instances 1322, the storage volumes, andtopology of the bundled application 1302.

Referring to FIG. 22, the illustrated configuration may be used inbundled applications including many, e.g. 10 s, 100 s, or 1000 s,instances of the same executable. In such cases, persistent data that isused and updated by each instance may be identical upon instantiation.This may include a root file system for the instance that is initiallypopulated with files.

In the illustrated embodiment, containers 2200 a-2200 c may executeinstances 2202 a-2202 c of the same executable. The containers 2200a-2200 b may be created and managed as part of a bundled applicationaccording to any of the embodiments disclosed herein.

Upon provisioning of storage for each instance 2202 a-2202 c, oneinstance 2202 a may be provisioned with a storage volume that is aprimary snapshot 2204 a for the storage volume. The primary snapshot2204 a may be populated with an initial image of a root file system forthe executable corresponding to the instance 2202 a.

The remaining instances 2202 b-2202 c may be provisioned with clonesnapshots 2204 b-2204 c of the storage volume. The snapshots 2204 b-2204c may be thin clone snapshots. In this manner, reads for data in theinitial image in a clone snapshot 2204 b-2204 c that has not beenoverwritten by an instances 2202 b-2202 c will be routed to the storagenode 106 storing the primary snapshot 2204 c, such as in the mannerdescribed with respect to the method 1200 of FIG. 12. The initial imagetherefore does not need to be copied into the storage provisioned foreach instance 2202 b-2202 c. This reduces the network traffic requiredby this copying, which would be extremely high upon creation of thebundled application including the instances 2220 a-2202 c. This copyingwould create a delay in the startup of a bundled application. Use ofthin clone snapshots as shown in FIG. 22 therefore speeds up thedeployment of a bundled application. The clone snapshots 2204 b-2204 cmay also be deferred thick clones (see discussion of some or all ofFIGS. 19A-19E) such that loading of the storage node 106 storing theprimary snapshot 2204 a will eventually be eliminated.

Referring to FIG. 23, in some embodiments, a bundled application 1302may be parameterized. For example, roles 1312 may be defined and one ormore parameters may define the number of instances of each role 1312(i.e., the number of containers executing an instance of a role 1312)and the amount of resources (storage, memory, cores) assigned to eachinstance of each role 1312. Likewise, an application instance 1322 mayinclude various user configurable parameters. Other user configurableparameters may include default passwords, or other user-configurablesettings.

Accordingly, the illustrated method 2300 may include receiving 2302 abundled application and configuring 2304 some or all of theseparameters. If a user is found 2306 to instruct saving of the bundledapplication as a template, then the bundled application is saved 2308.In particular, the bundled application and any parameters configured bya user at step 2304 are saved. In this manner, any number of instancesof the bundled application as configured at step 2304 may be deployed atany number of locations without having to repeatedly specify theparameters.

In one use case, a user may create multiple templates, each with adifferent set of parameters. For example, a bundled application with acertain number of instances of various roles and corresponding resourcesmay be saved as a “small” template. The bundled application with agreater number of instances of the various roles and correspondingresources may be saved as a “large” template. Of course, any number oftemplates with any number of variation in the number of instances may besaved.

The bundled application as configured at step 2304 may then be deployed2310, such as according to the approach described above with respect toFIG. 14.

Referring to FIG. 24, deployment of a bundled application 1302 mayinclude processing the manifest 1304 that defines the instances of eachrole 1312 and the dependency between roles 1312. Dependency may bespecified at various stages of deployment, such as creation of roles,e.g., instantiation of containers 1320 and loading of applicationinstances 1322 into containers 1320, starting of roles 1312, e.g.,commencement of execution of containers 1320, or the like. Other actionsfor which dependency may be specified may include stopping andrestarting of roles 1312. The dependency may be specified by a developerof the bundled application 1302.

The manifest 1304 may have various forms as specified by a developer.For example, an order of creation and starting of roles may be specifiedexplicitly, which is referred to herein as a “serialized” ordering.Accordingly, a manifest 1304 may include a listing of roles and aninstruction to create them that is preceded by a “serialized” tagindicating that the roles are to be created in series. In a like manner,a listing roles with an instruction to start them could be associatedwith a “parallelized” tag and therefore be started in that order. Whereinstructions are tagged as “serialized,” each instruction may bepermitted to execute only after a preceding instruction has completedexecution.

In another form, instructions to take an action with respect to multipleroles may be specified to be “parallelized,” such as by associating atag with a listing of instructions. In this case, the instruction may beprocessed in parallel. Constraints on parallel execution of instructionsmay be specified by defining a dependency. For example, for roles RA andRB, a dependency may be specified as RA: depends_on(RB). In this case,an action (create, start, stop, restart, etc.) will not be performed forRA until this action is completed for RB.

A bundled application 1302 may include multiple roles and each role mayitself include multiple components or multiple actions that are part ofa given application-wide action (create, start, stop, restart, etc.).Creation of a container for a role may likewise include multiplecomponents or multiple actions that are part of implementing a givenapplication-wide action. A bundled application 1302 may likewise definesub-bundles of roles.

The manifest 1304 may therefore define a dependency map that defines ahierarchy wherein each node of the hierarchy specifies performance of anaction (create, start, stop, restart) with respect to one or moreentities as being serialized, parallelized, and possibly subject todependency among entities. The type of ordering (serialized orparallelized) for a node may be the same as or different from the typeof ordering for a parent node in the hierarchy.

Each entity may then itself be a specific executable instance or a subnode for which the action is to be performed subject to the specifiedordering. An entity that is a sub-node may include the specification ofan action with respect to multiple other entities as being serialized,parallelized, and possibly imposes dependency. A sub node may thereforeinclude a specification of an order of execution (serialized,parallelized, subject to dependency) of an action for an entireapplication, a bundle of roles, a specific role, multiple instances ofthe same role, or components of an individual container.

For example, as shown in FIG. 24, the specification of anapplication-wide action 2400 (create, start, stop, restart, etc.) mayinclude a parameter 2402 indicating whether the application-wide action2400 is serialized or parallel. The specification 2400 may furtherinclude one or more roles 2404 for which the action will be taken. Arole 2404 may define one or more dependencies 2406 with respect to oneor more others of the roles 2404. Accordingly, the action will be takenwith respect to each role 2404 either (a) in the order specified wherethe parameters 2402 indicates serialized execution or (b) in parallelsubject to dependency constraints 2406.

Taking the action with respect to a role 2404 may include executing arole-specific action 2408. For example, where the action 2400 iscreating the bundled application, the role specific action 2408 may becreating the role 2404.

The specification 2408 may include a parameters 2410 indicating that theaction 2408 is serialized or parallel, which may be the same as ordifferent from the parameter 2402. The specification 2408 may furtherinclude a listing of one or more components 2412. One or more components2412 may include a dependency 2414 on one or more others of thecomponents 2412. Components may include different executable componentsof an application instance, different instances of the same application(e.g. where a role includes multiple instances of the same application),containers, or a component of a container.

Where a component 2412 is a container, a container-specific action 2406may be executed for that component 2412, which may include its ownparameter 2412 specifying whether it is serialized or parallel and oneor more components 2412 of the container for which the action is to beperformed. As for other levels of the hierarchy, dependency 2412 betweencomponents of the container may be specified.

Accordingly, execution of a manifest 1304 or a hook 1310 defining anaction may include traversing a hierarchy, such as that illustrated inFIG. 24. The application-wide specification 2402 may be executed, whichmay include executing the role-specific actions 2408 in the orderspecified or in parallel subject to the dependencies 2414. Executingrole-specific actions 2408 may include executing the container-specificactions 2416 for each component 2412 subject to the dependencies 2414 orin series where specified.

Executing the container specific actions 2416 may include executing themfor one or more components 2420 of the container in an order(serialized/parallelized) specified by a parameter 2418, possiblysubject to one or more dependencies 2422 among components.

FIG. 25 is a block diagram illustrating an example computing device2500. Computing device 2500 may be used to perform various procedures,such as those discussed herein. The storage manager 102, storage nodes106, compute nodes 110, and hybrid nodes, may have some or all of theattributes of the computing device 2500.

Computing device 2500 includes one or more processor(s) 2502, one ormore memory device(s) 2504, one or more interface(s) 2506, one or moremass storage device(s) 2508, one or more Input/output (I/O) device(s)2510, and a display device 2530 all of which are coupled to a bus 2512.Processor(s) 2502 include one or more processors or controllers thatexecute instructions stored in memory device(s) 2504 and/or mass storagedevice(s) 2508. Processor(s) 2502 may also include various types ofcomputer-readable media, such as cache memory.

Memory device(s) 2504 include various computer-readable media, such asvolatile memory (e.g., random access memory (RAM) 2514) and/ornonvolatile memory (e.g., read-only memory (ROM) 2516). Memory device(s)2504 may also include rewritable ROM, such as Flash memory.

Mass storage device(s) 2508 include various computer readable media,such as magnetic tapes, magnetic disks, optical disks, solid-statememory (e.g., Flash memory), and so forth. As shown in FIG. 25, aparticular mass storage device is a hard disk drive 2524. Various drivesmay also be included in mass storage device(s) 2508 to enable readingfrom and/or writing to the various computer readable media. Mass storagedevice(s) 2508 include removable media 2526 and/or non-removable media.

I/O device(s) 2510 include various devices that allow data and/or otherinformation to be input to or retrieved from computing device 2500.Example I/O device(s) 2510 include cursor control devices, keyboards,keypads, microphones, monitors or other display devices, speakers,printers, network interface cards, modems, lenses, CCDs or other imagecapture devices, and the like.

Display device 2530 includes any type of device capable of displayinginformation to one or more users of computing device 2500. Examples ofdisplay device 2530 include a monitor, display terminal, videoprojection device, and the like.

Interface(s) 2506 include various interfaces that allow computing device2500 to interact with other systems, devices, or computing environments.Example interface(s) 2506 include any number of different networkinterfaces 2520, such as interfaces to local area networks (LANs), widearea networks (WANs), wireless networks, and the Internet. Otherinterface(s) include user interface 2518 and peripheral device interface2522. The interface(s) 2506 may also include one or more peripheralinterfaces such as interfaces for printers, pointing devices (mice,track pad, etc.), keyboards, and the like.

Bus 2512 allows processor(s) 2502, memory device(s) 2504, interface(s)2506, mass storage device(s) 2508, I/O device(s) 2510, and displaydevice 2530 to communicate with one another, as well as other devices orcomponents coupled to bus 2512. Bus 2512 represents one or more ofseveral types of bus structures, such as a system bus, PCI bus, IEEE1394 bus, USB bus, and so forth.

For purposes of illustration, programs and other executable programcomponents are shown herein as discrete blocks, although it isunderstood that such programs and components may reside at various timesin different storage components of computing device 2500, and areexecuted by processor(s) 2502. Alternatively, the systems and proceduresdescribed herein can be implemented in hardware, or a combination ofhardware, software, and/or firmware. For example, one or moreapplication specific integrated circuits (ASICs) can be programmed tocarry out one or more of the systems and procedures described herein.

In the above disclosure, reference has been made to the accompanyingdrawings, which form a part hereof, and in which is shown by way ofillustration specific implementations in which the disclosure may bepracticed. It is understood that other implementations may be utilizedand structural changes may be made without departing from the scope ofthe present disclosure. References in the specification to “oneembodiment,” “an embodiment,” “an example embodiment,” etc., indicatethat the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

Implementations of the systems, devices, and methods disclosed hereinmay comprise or utilize a special purpose or general-purpose computerincluding computer hardware, such as, for example, one or moreprocessors and system memory, as discussed herein. Implementationswithin the scope of the present disclosure may also include physical andother computer-readable media for carrying or storingcomputer-executable instructions and/or data structures. Suchcomputer-readable media can be any available media that can be accessedby a general purpose or special purpose computer system.Computer-readable media that store computer-executable instructions arecomputer storage media (devices). Computer-readable media that carrycomputer-executable instructions are transmission media. Thus, by way ofexample, and not limitation, implementations of the disclosure cancomprise at least two distinctly different kinds of computer-readablemedia: computer storage media (devices) and transmission media.

Computer storage media (devices) includes RAM, ROM, EEPROM, CD-ROM,solid state drives (“SSDs”) (e.g., based on RAM), Flash memory,phase-change memory (“PCM”), other types of memory, other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium which can be used to store desired program code means inthe form of computer-executable instructions or data structures andwhich can be accessed by a general purpose or special purpose computer.

An implementation of the devices, systems, and methods disclosed hereinmay communicate over a computer network. A “network” is defined as oneor more data links that enable the transport of electronic data betweencomputer systems and/or modules and/or other electronic devices. Wheninformation is transferred or provided over a network or anothercommunications connection (either hardwired, wireless, or a combinationof hardwired or wireless) to a computer, the computer properly views theconnection as a transmission medium. Transmissions media can include anetwork and/or data links, which can be used to carry desired programcode means in the form of computer-executable instructions or datastructures and which can be accessed by a general purpose or specialpurpose computer. Combinations of the above should also be includedwithin the scope of computer-readable media.

Computer-executable instructions comprise, for example, instructions anddata which, when executed at a processor, cause a general purposecomputer, special purpose computer, or special purpose processing deviceto perform a certain function or group of functions. The computerexecutable instructions may be, for example, binaries, intermediateformat instructions such as assembly language, or even source code.Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the described features or acts described above.Rather, the described features and acts are disclosed as example formsof implementing the claims.

Those skilled in the art will appreciate that the disclosure may bepracticed in network computing environments with many types of computersystem configurations, including, an in-dash vehicle computer, personalcomputers, desktop computers, laptop computers, message processors,hand-held devices, multi-processor systems, microprocessor-based orprogrammable consumer electronics, network PCs, minicomputers, mainframecomputers, mobile telephones, PDAs, tablets, pagers, routers, switches,various storage devices, and the like. The disclosure may also bepracticed in distributed system environments where local and remotecomputer systems, which are linked (either by hardwired data links,wireless data links, or by a combination of hardwired and wireless datalinks) through a network, both perform tasks. In a distributed systemenvironment, program modules may be located in both local and remotememory storage devices.

Further, where appropriate, functions described herein can be performedin one or more of: hardware, software, firmware, digital components, oranalog components. For example, one or more application specificintegrated circuits (ASICs) can be programmed to carry out one or moreof the systems and procedures described herein. Certain terms are usedthroughout the description and claims to refer to particular systemcomponents. As one skilled in the art will appreciate, components may bereferred to by different names. This document does not intend todistinguish between components that differ in name, but not function.

It should be noted that the sensor embodiments discussed above maycomprise computer hardware, software, firmware, or any combinationthereof to perform at least a portion of their functions. For example, asensor may include computer code configured to be executed in one ormore processors, and may include hardware logic/electrical circuitrycontrolled by the computer code. These example devices are providedherein purposes of illustration, and are not intended to be limiting.Embodiments of the present disclosure may be implemented in furthertypes of devices, as would be known to persons skilled in the relevantart(s).

At least some embodiments of the disclosure have been directed tocomputer program products comprising such logic (e.g., in the form ofsoftware) stored on any computer useable medium. Such software, whenexecuted in one or more data processing devices, causes a device tooperate as described herein.

While various embodiments of the present disclosure have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the disclosure.Thus, the breadth and scope of the present disclosure should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents. The foregoing description has been presented for thepurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. Further, it should be noted that any or all of theaforementioned alternate implementations may be used in any combinationdesired to form additional hybrid implementations of the disclosure.

The invention claimed is:
 1. A method comprising: storing first datafrom first write requests referencing a first storage volume in firstsegments on a first storage node, the first segments being mapped to afirst snapshot of the first storage volume; receiving, by the firststorage node, a request to create a second snapshot that is a clone ofthe first snapshot; subsequent to receiving the request, receivingsecond write requests referencing the first storage volume; storingsecond data from the second write requests in second segments mapped tothe second snapshot of the first storage volume, the second segmentsbeing on a second storage node different from the first storage node;subsequent to receiving the request, receiving, by the second storagenode, a first read request referencing the first data and the secondsnapshot; (a) determining, by the second storage node, that the firstdata is not stored on the second storage node; in response to (a),transmitting, by the second storage node, the first read request to thefirst storage node for execution; subsequent to receiving the request,receiving, by the second storage node, a second read request referencingthe second data and the second snapshot; (b) determining, by the secondstorage node, that the second data is stored on the second storage node;and in response to (b), executing the second read request by the secondstorage node; wherein: the first segments and second segments are partof a database defining a name space; the request includes a definitionof a portion of the name space that is less than an entirety of the namespace; the second write requests reference the portion of the namespace; and the method further comprises copying, subject to a load limitof the first storage node, a portion of the first segments includingdata referenced by the portion of the name space and refraining fromcopying a portion of the first segments that do not include datareferenced by the portion of the name space.
 2. The method of claim 1,further comprising: in response to (a), transmitting, by the firststorage node, a clone write request to the second storage node, theclone write request referencing the second snapshot and including datareferenced by the first read request; and executing, by the firststorage node, the clone write request.
 3. The method of claim 1, furthercomprising, in response to (a): incrementing a counter; and when thecounter meets a threshold condition, copying a portion of the firststorage volume to the second storage node, the portion including datareferenced by the first read request and additional data from the firststorage volume.
 4. The method of claim 1, further comprising: copying,from the first storage node to the second storage node, the firstsegments.
 5. The method of claim 1, further comprising: copying, fromthe first storage node to the second storage node, the first segmentssubject to a load limit on the first storage node.
 6. The method ofclaim 1, further comprising: copying, from the first storage node to thesecond storage node, the first segments during a specified time periodduring which the first storage node is unloaded.
 7. The method of claim1, further comprising: copying, from the first storage node to thesecond storage node, a first portion the first segments subject to afirst load limit on the first storage node; detecting unloading of thefirst storage node; and in response to detecting unloading of the firststorage node, copying, from the first storage node to the second storagenode, a second portion of the first segments subject to a second loadlimit that is higher than the first load limit.
 8. The method of claim1, further comprising: evaluating, by the second storage node, afrequency of read requests with respect to the first segments; identify,by the second storage node, a first portion of the first segments thathave a higher frequency of read requests than a remaining portion of thefirst segments; and copying, by the second storage node, the firstportion of the first segments to the second storage node prior to theremaining portion of the first segments subject to a load limit.
 9. Asystem comprising: a network; a plurality of storage nodes operablycoupled to the network; a plurality of compute nodes operably coupled tothe network; a storage manager computer comprising one or moreprocessing devices and one or more memory devices operably coupled tothe one or more processing devices, the one or more memory devicesstoring executable code effective to cause the one or more processingdevices to: invoke storage of first data from first write requestsreferencing a first storage volume in first segments on a first storagenode, the first segments being mapped to a first snapshot of the firststorage volume; receive a request to create a second snapshot that is aclone of the first snapshot; and subsequent to receiving the request,invoke storing second data from second write requests referencing thefirst storage volume in second segments mapped to the second snapshot ofthe first storage volume, the second segments being on a second storagenode different from the first storage node; wherein the second storagenode is further programmed to: subsequent to receiving the request,receive a second read request referencing the second data and the secondsnapshot; (b) determine that the second data is stored on the secondstorage node; and in response to (b), executing the second read requestby the second storage node; wherein the second storage node isprogrammed to: subsequent to receiving the request, receive a first readrequest referencing the first data and the second snapshot; (a)determine that the first data is not stored on the second storage node;and in response to (a), transmit the first read request to the firststorage node for execution; and wherein: the first segments and secondsegments are part of a database defining a name space; the requestincludes a definition of a portion of the name space that is less thanan entirety of the name space; the second write requests reference theportion of the name space; and the second storage node is furtherprogrammed to, subject to a load limit of the first storage node, copy aportion of the first segments including data referenced by the portionof the name space and refraining from copying a portion of the firstsegments that do not include data referenced by the portion of the namespace.
 10. The system of claim 9, wherein the second storage node isfurther programmed to: copy the first segments from the first storagenode to the second storage node.
 11. The system of claim 9, wherein thesecond storage node is further programmed to: copy the first segmentsfrom the first storage node to the second storage node subject to a loadlimit on the first storage node.
 12. The system of claim 9, wherein thesecond storage node is further programmed to: copy the first segmentsfrom the first storage node to the second storage node during aspecified time period during which the first storage node is unloaded.13. The system of claim 9, wherein the second storage node is furtherprogrammed to: copy, from the first storage node to the second storagenode, a first portion the first segments subject to a first load limiton the first storage node; detect unloading of the first storage node;and in response to detecting unloading of the first storage node, copy,from the first storage node to the second storage node, a second portionof the first segments subject to a second load limit that is higher thanthe first load limit.
 14. The system of claim 9, wherein the secondstorage node is further programmed to: evaluate a frequency of readrequests with respect to the first segments; identify a first portion ofthe first segments that have a higher frequency of read requests than aremaining portion of the first segments; and copy the first portion ofthe first segments to the second storage node prior to the remainingportion of the first segments subject to a load limit.